This shiny penny science experiment is fun for kids of all ages. I love that you can make the pennies look better or worse! You might also enjoy these STEM activities for kids using household items.

Penny Science Experiment for Kids
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This simple science experiment is fun, costs pennies, and can be done, reversed, and done again. Pretty magical!
Research Question: Why Does Copper Turn Green?
Have you ever seen a building with a copper roof that was green? The Statue of Liberty is also green because it is made out of copper. This thoroughly confused me as a child, because I knew very well that it was copper that gave pennies their distinct, very un-green color.
Copper turns green after reacting with oxygen. And that green patina actually protects copper from corrosion!
Experiment #1: Pennies and Vinegar
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As an oxidation experiment, we took some shiny pennies and laid them on a vinegar-soaked paper towel. After a couple of days, they turned quite green on the face-up side.

The vinegar only sped up the oxidation of the pennies where the pennies were in contact with the vinegar. The pennies stayed shiny on the side that was against the paper towel.
Science Experiment #2: Pennies and Olive Oil
We wanted to find out if we could then remove that patina.

We took our vinegar pennies and soaked them in olive oil for a couple of days, because I know that’s one way you can clean very old coins.
The “green” side looked a little more metallic, although the pennies definitely showed some marking from their journey.

The “shiny” side actually looked a little worse, especially where a couple pennies had overlapped by accident during the vinegar portion of the experiment!
Next time we’ll try lemon juice and salt for a couple days, like we read about at sunnydaytodaymama.
Have you tried this shiny penny science experiment? What did you discover?
More Science Activities for Kids
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MaryAnne is a craft loving educator, musician, photographer, and writer who lives in Silicon Valley with her husband Mike and their four children.
We did ketchup and was amazed at the difference.
I need to try that!
Fantastic experiment!
Kerri
OH, this is a fun one here too! Haven’t done it with Jack yet, so thank you for the reminder!
This is something I’ve wanted to do for about 3 years, but never have. Thanks for the reminder. :)
I know a couple of people have linked up with penny leaning experiments on science Sunday I’ve seen ketchup used and UT worked fairly fast
Looks like you had some interesting results from your experiments! Sunnyboy will enjoy giving these methods a try. Thanks for linking to our cleaning coins post. :)
I didn’t know that the pennies will get green – wouldn’t it apply only to really old pennies that were still made with copper? I recall reading somewhere that newer pennies don’t have copper in them. We tried to clean our pennies in vinegar solution – this was a big hit.
@Natalie – These were new(ish) pennies, and they still turned green – at least three. I think they are still copper-plated?
Have you seen this website with ideas of how to clean pennies? We might try some of them:
http://www.pennycollector.com/tips_clean.html
We have a zillion pennies in piggy banks, jars, etc., so I’ll have to try this. I think my daughters might have the patience for it.
How interesting! I always learn something from your experiments.
I really like this experiment! But I know my girls will have no patience for it whatsoever! (Can I just send you my pennies to clean! ha! ha!)